The present invention relates to an infinitely variable power bypass transmission with two operating modes for a motor vehicle fitted with an internal, combustion engine.
Such a power bypass transmission makes it possible to obtain a continuous variation from a reverse ratio to a forward ratio, passing through a particular position called “neutral engaged”, in which the speed of movement of the vehicle is zero, for any speed of the internal combustion engine.
There are several types of power bypass transmissions.
According to a first type called “coupled input”, the transmission comprises a pair of power bypass pinions which bypass the power at the input of the mechanism and a “combining” epicyclic gear train which recombines the powers at the output of the mechanism. The transmission also comprises a speed variator.
In another type called “coupled output”, the transmission comprises a power dividing epicyclic gear train at the input of the mechanism and a pair of power combining pinions at the output of the mechanism. The transmission also comprises a speed variator.
Finally, power bypass transmissions called “two adaptation points” transmissions are known in which a first power dividing epicyclic gear train is placed at the input of the transmission, while a second power combining epicyclic gear train is mounted at the output of the transmission. There again, the transmission comprises a speed variator.
An infinitely variable transmission (IVT) uses only one or two of these three operating principles.
The present invention relates to an infinitely variable transmission using two distinct operating modes and comprising a mode-changing device making it possible to switch from a first operating mode to a second operating mode.
It is understood that it is of value to have two operating modes for one and the same transmission, because that makes it possible to increase the range of transmission ratios and also makes it possible to reduce the dimensions of the speed variator device which may comprise electric machines.
Such bi-mode transmission architectures of known type however have the disadvantage that the mode changes are carried out by multi-disk clutches placed at the transmission output, so that their operation is accompanied by sharp torque variations that are unpleasantly felt by the users. Another disadvantage of such a transmission described for example in U.S. Pat. No. 5,558,589 or in U.S. Pat. No. 5,935,035 lies in the complexity of the architecture, associated particularly with the presence of at least two clutches and a brake.
In a previous French patent application FR 02 14 241 in the name of the applicant, a description was given of an infinitely variable transmission with two operating modes, of the type comprising an electric variator and at least two power bypass lines, a main line whereof connects the internal combustion engine to the drive wheels, and a secondary line is connected to the electric variator, so that at least two operating modes may be applied to the power bypass line of the electric variator.
The infinitely variable transmission described in this prior patent application comprises a first composite epicyclic gear train which makes it possible to connect the internal combustion engine to the wheels of the vehicle along a main power bypass line and a simple epicyclic gear train which makes it possible to achieve the power bypass and a second composite epicyclic gear train, so as to produce a mode-changing system between at least two operating modes of the infinitely variable transmission.
The transmission described in this prior patent application comprises two coupling/decoupling devices which allow two transmission shafts to be independently locked or released in rotation, thereby each time providing one of the operating modes of the transmission.
During a mode change, the two coupling/decoupling devices are controlled independently by two actuators which may be moved by an electric force or a hydraulic force. The two actuators are controlled so that the two modes are engaged simultaneously, the aforementioned two shafts of the transmission being simultaneously locked in rotation.